This program is directed at the elucidation of the role of the renin-angiotensin system and other factors in the regulation of aldosterone secretion by the zona glomerulosa of the adrenal gland. Specific areas of research include the characterization and regulation of angiotensin II receptors, the actions of angiotensin II and other regulators of aldosterone secretion, and the production and metabolism of angiotensin II. Major emphasis has been placed upon the use of enzyme-dispersed adrenal cells for analysis of the relations between angiotensin II receptors and aldosterone production, and the interactions between angiotensin II and other factors such as ACTH, sodium and potassium levels. Studies on the effects of chronic electrolyte imbalance on adrenal receptors and steroid responses were extended to show important acute effects of sodium balance on the concentration and affinity of angiotensin II receptors in adrenal and uterine smooth muscle. These results are relevant to changes in adrenal and vascular sensitivity to angiotensin II during sodium deficiency. These studies have also shown that angiotensin II acts to regulate the concentration of its own receptors in adrenal and smooth muscle. BIBLIOGRAPHIC REFERENCES: Catt, K.J., Saltman, S., Douglas, J., and Kondo, T.: Competitive antagonists of angiotensin II: Inhibition of receptor binding and aldosterone production in dispersed adrenal cells. In Systemic Effects of Antihypertensive Agents (Ed. M.P. Sambhi) Symposia Specialists, Miami, 1976, pp. 425-439. Fredlund, P., Saltman, S., Kondo, T. and Catt, K.J.: Aldosterone production by isolated glomerulosa cells: Modulation of sensitivity of angiotensin II by extracellular potassium interaction. Endocrinology 100: 481-486, 1977.